42 research outputs found
Decoupled black hole accretion and quenching : the relationship between BHAR, SFR and quenching in Milky Way- and Andromeda-mass progenitors since z=2.5
We investigate the relationship between the black hole accretion rate (BHAR) and star formation rate (SFR) for Milky Way (MW) and Andromeda (M31)-mass progenitors from z = 0.2 to 2.5. We source galaxies from the K-s-band-selected ZFOURGE survey, which includes multiwavelength data spanning 0.3-160 mu m. We use decomposition software to split the observed spectral energy distributions (SEDs) of our galaxies into their active galactic nuclei (AGNs) and star-forming components, which allows us to estimate BHARs and SFRs from the infrared (IR). We perform tests to check the robustness of these estimates, including a comparison with BHARs and SFRs derived from X-ray stacking and far-IR analysis, respectively. We find that, as the progenitors evolve their relative black hole-galaxy growth (i.e. their BHAR/SFR ratio) increases from low to high redshift. The MW-mass progenitors exhibit a log-log slope of 0.64 +/- 0.11, while the M31-mass progenitors are 0.39 +/- 0.08. This result contrasts with previous studies that find an almost flat slope when adopting X-ray-/AGN-selected or mass-limited samples and is likely due to their use of a broad mixture of galaxies with different evolutionary histories. Our use of progenitor-matched samples highlights the potential importance of carefully selecting progenitors when searching for evolutionary relationships between BHAR/SFRs. Additionally, our finding that BHAR/SFR ratios do not track the rate at which progenitors quench casts doubts over the idea that the suppression of star formation is predominantly driven by luminous AGN feedback (i.e. high BHARs)
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SATELLITE QUENCHING and GALACTIC CONFORMITY at 0.3 < z < 2.5
We measure the evolution of the quiescent fraction and quenching efficiency of satellites around star-forming and quiescent central galaxies with stellar mass at . We combine imaging from three deep near-infrared-selected surveys (ZFOURGE/CANDELS, Ultra Deep Survey, and UltraVISTA), which allows us to select a stellar-mass complete sample of satellites with . Satellites for both star-forming and quiescent central galaxies ("centrals") have higher quiescent fractions compared to field galaxies matched in stellar mass at all redshifts. We also observe "galactic conformity": satellites around quiescent centrals are more likely to be quenched compared to the satellites around star-forming centrals. In our sample, this conformity signal is significant at for , whereas it is only weakly significant at and . Therefore, conformity (and thus satellite quenching) has been present for a significant fraction of the age of the universe. The satellite quenching efficiency increases with increasing stellar mass of the central, but does not appear to depend on the stellar mass of the satellite to the mass limit of our sample. When we compare the satellite quenching efficiency of star-forming centrals with stellar masses 0.2 dex higher than quiescent centrals (which should account for any difference in halo mass), the conformity signal decreases, but remains statistically significant at . This is evidence that satellite quenching is connected to the star formation properties of the central galaxy as well as to the mass of the halo. We discuss physical effects that may contribute to galactic conformity, and emphasize that they must allow for continued star formation in the central galaxy even as the satellites are quenched